The proposed study is designed to assess the effects of resistance training on body composition and energy and protein metabolism changes during weight loss in older women provided a defined nutrient diet. Body composition, muscle strength, size and function, resting energy expenditure, nitrogen balance and whole-body and muscle protein kinetics also will be examined. Primary measures of interest are protein metabolism and body composition. We hypothesize that weight reduction in moderately overweight older women by dietary energy restriction alone will results in reductions in FFM, whole body protein mass and muscle mass. Resistance training , with or without dietary energy restriction, will preserve or enhance FFM, whole body protein mass and muscle mass. Diet-induced weight loss in older women will reduce whole-body nitrogen balance, lowere rates of whole body protein turnover, and decrease the rate of muscle protein sysnthesis. Resistance training, with or without a hypocaloric diet, will preserve or enhance these indices of protein metabolism. Weight loss from energy restriction without resistance training will result in significant reductions in testing metabolic rate while resistance training, with or without energy retriction, will preserve rates of energy metabolism. Weight loss via energy restriction without resistance training will result in significant declines in muscle strength, muscle power and muscle function. Resistance training, with or without hypocaloric diet, will enhance muscle stremngth and preserve muscle power and muscle function.